4.5: Measurement of Gaseous Emissions from Animal Housing
Mélynda Hassouna
UMR Sol, Agro et hydrosystèmes et Spatialisation, INRAe, Agrocampus, France
Salvador Calvet
Institute of Animal Science and Technology, Universitat Politècnica de València, Valencia, Spain
Richard S. Gates
Agricultural & Biosystems Engineering, and Animal Sciences, Iowa State University, Ames, Iowa, USA
Enda Hayes
Air Quality Management Resource Centre, Department of Geography and Environmental Management, University of the West of England, Bristol, United Kingdom
Sabine Schrade
Ruminants Research Unit, Federal Department of Economic Affairs, Education and Research EAER, Agroscope, Ettenhausen, Switzerland
| Key Terms |
| Emission processes | Mass balance | Ammonia |
| Measurement techniques | Validation | Greenhouse gases |
| Sampling | Ventilation |
Variables
Introduction
Animal housing and manure storage facilities are two principal on-farm sources of gaseous emissions to the atmosphere. The most important pollutants emitted are ammonia (NH 3 ), methane (CH 4 ), and nitrous oxide (N 2 O).
Ammonia (NH 3 ) is a colorless gas with a pungent smell that can have impacts on environmental and human health (Figure 4.5.1). Ammonia is emitted by many agricultural activities, including crop production as well as animal production. Ammonia plays a key role in the formation of secondary particulate matter (PM) by reacting with acidic species such as sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) to form fine aerosols, and is thus called a particulate precursor. The PM created by the reaction of NH 3 and acidic species in the atmosphere contributes to poor air quality including regional haze. These particles have an aerodynamic diameter of less than 2.5 microns and are generally referred to as “PM-fine.” They are readily inhaled and populations exposed to PM-fine have greater respiratory and cardiovascular health risks such as asthma, bronchitis, cardiac arrythmia and arrest, and premature death. Some emitted NH 3 is subsequently deposited on land and water downwind of facilities, and can acidify soils and freshwater. The addition of available nitrogen (N) to low-nutrient ecosystems disturbs their balance and can alter the relative growth and abundance of plant species.
Nitrous oxide and CH 4 are potent greenhouse gases (GHGs) which contribute to global warming. The global warming potential (GWP) is a factor specific to each GHG and allows comparisons of the relative global warming impacts between different GHGs. This factor indicates how much heat a given gas traps over a certain time horizon (usually 100 years), compared with an equal mass of carbon dioxide (CO 2 ). Nitrous oxide GWP for a 100-year time horizon is 265 with a lifetime in the atmosphere of 114 years. Methane GWP for a 100-year time horizon is 28 with a lifetime in the atmosphere of 12 years.
Nitrous oxide, also known as “laughing gas,” is colorless and odorless, and contributes to the destruction of the atmospheric ozone layer. In agriculture, the main source of N 2 O emissions is soil, from crop fertilizer use, soil cultivation, and spreading of urine and manure. Other sources include industrial processes, and natural processes involving soils and oceans.
Methane is a volatile organic compound, odorless and flammable. In agriculture, the main sources are enteric fermentation (fermentation that takes place in the digestive systems of animals) and the degradation of manure. Methane contributes to ozone formation in the lower atmosphere, and to ozone layer depletion in the upper atmosphere.
Researchers and engineers have developed different approaches to reliably measure and quantify emissions of NH 3 , N 2 O, and CH 4 from animal production facilities. The implementation of these methods helps to understand the production processes, to identify the influencing factors, and to develop mitigation techniques or practices. The specific characteristics of animal housing and the variability of the houses and animal production systems make the development and implementation of the different methods a real challenge.
Concepts
Animal Houses
Animal housing is designed to provide shelter and protection with control of feed consumption, diseases, parasites, and the interior thermal environment. An animal house is designed to take into account animal heat and moisture production, building characteristics (e.g., insulation and volume), and outdoor climate. Inside the house, animals produce the following critical components that affect emissions:
- • sensible heat that is transferred to the interior air by means of convection, conduction, and radiation, and causes an increase of air temperature;
- • latent heat that is generated through the evaporation of moisture from the lungs, skin, urine, and fecal material, and through increases of air humidity;
- • mixtures of feces and urine, which become a source of gaseous emissions (NH 3 , N 2 O, CO 2 , water vapor, CH 4 ), and heat; and
- • CO 2 from animal respiration.
The control of temperature, moisture, gas concentrations and dust concentrations inside the house is essential to achieve optimal conditions for animal growth and production. The optimal conditions vary as a function of animal age, species, and breed, and rely on the implementation of ventilation systems. The ventilation system partly controls the rate and total emissions from the building. There are two types of ventilation systems: mechanical and natural. The RAMIRAN European network (RAMIRAN, 2011) defines the two systems as:
- • mechanical ventilation, which is ventilation of a building, usually for pigs, poultry, or calves, through the use of electrically powered fans in the walls or roof that are normally controlled by the temperature in the building; and
- • natural ventilation, which is ventilation of a building, e.g., for cattle, by openings or gaps designed into the roof and/or sides of the building.
NH 3 , N 2 O, and CH 4 Emissions Processes in Animal Housing and Influencing Factors
Ammonia is volatilized as a gas during manure management. It is mainly derived from the urea excreted in urine (or uric acid in the feces, in the case of poultry). The process of forming NH 3 from urea is relatively fast and is outlined in Figure 4.5.2. Once excreted, urea is decomposed within a few hours to a few days into ammonium (NH 4 ) by means of the enzyme urease, which is widely present in feces and soils. Ammonium is in equilibrium with dissolved NH 3 enhanced at high pH values. A second physical equilibrium exists between dissolved and free NH 3 in the manure matrix. Finally, the free NH 3 can be released to the atmosphere. This is a mass transfer process affected by air velocity, diffusion from beneath the surface, and exposure to air on the surface of the manure.
This is a continuous process that starts in the animal housing itself and continues during manure management and land application. Several factors are involved in the amount of NH 3 emitted to the atmosphere:
- • manure composition; the most relevant factors are the amount of urea excreted by the animals, the pH of the manure, and its moisture content;
- • the environmental conditions, particularly temperature and wind speed above the emitting surface;
- • the facilities for animal housing and manure management; and
- • management practices, particularly those altering the contact of manure with air, and urine with feces, by reducing time of exposure or contact surface.
On farms, N 2 O originates from the management of manure and its application to land as fertilizer. Emission of N 2 O occurs from the successive nitrification and denitrification of NH 4 . A first aerobic phase is required for the nitrification, while anoxic conditions are required for denitrification (Figure 4.5.3). These conditions are characteristic of the following situations:
- • composting with alternative wetting, mixing, and drying periods;
- • aerobic treatment of slurry;
- • air cleaners at the air exhaust of the animal house based on biological scrubbing of air; and
- • application of manure to soil and subsequent drying-wetting events.
Methane is produced during the anaerobic decomposition of organic matter. This occurs mainly during digestion in ruminants and decomposition of manure. In this process, the microbial breakdown of organic matter occurs in different stages, from more complex molecules to the simplest. The main mechanism is presented in Figure 4.5.4. Apart from the presence of organic matter and anoxic conditions, time (a few weeks) is needed to complete the process, and the process may be inhibited due to certain conditions, such as NH 3 accumulation. In contrast to NH 3 , CH 4 has very low solubility in water and, once produced, is released to the atmosphere through a characteristic bubbling, in the case of slurries.
For enteric fermentation in ruminants, key factors are feed composition and genetics. More digestible feeds reduce the amount of CH 4 . Feed constituents such as lipids or essential oils may reduce CH 4 production through inhibition. Genetics also influence the amount of CH 4 produced and can be modified through animal genetic selection.
CH 4 emission during manure management is due to the presence of organic matter subjected to anaerobic conditions for sufficient time (about one month, at least) for methanogenic bacteria to develop. The amount and composition of organic matter determines the maximum potential for CH 4 formation. Manure management practices that interrupt anaerobic conditions, reduce the load of organic matter, or feature biogas capture are potentially effective for mitigating emissions.
Measuring Emissions from Animal Housing
The most common approach used to determine gas emission rates from animal houses is based on quantifying ventilation rates and inlet and outlet concentrations of the gas (Figure 4.5.5). The mass flow rate of emitted gas (emission rate or ER ) is proportional to the ventilation rate and the concentration difference between exhaust and outside air. Several different techniques are available to measure gas concentrations inside and outside the house and the ventilation rate.
Gas Concentration Measurement Techniques
The techniques used most often to measure NH 3 , CH 4 , and N 2 O concentrations of animal houses are either physical (optical, gas chromatography, chemiluminescence) or chemical (acid traps, active colorimetric tubes).
Optical Techniques
Optical techniques are based on the Beer-Lambert absorption law, which indicates that the quantity of light of a given wavelength absorbed is related to the number of gas molecules in the light’s path that are able to absorb it.
Optical techniques rely on the use of a light source, a chamber to contain the air sample during measurement, and a detector to quantify the target gas absorption. The main techniques used in animal houses are infrared (IR) spectroscopy (photoacoustic or Fourier transform), tunable diode laser absorption spectroscopy (TDLAS), off-axis integrated cavity output spectroscopy (OA-ICOS), and cavity ring-down spectroscopy (CRDS). Differences between these techniques include the detection principle of absorption and the type and wavelength of light sources (quantum cascade laser, tunable diode laser, or IR source). Techniques using lasers (a monochromatic source with a narrow band of wavelengths) are more selective, accurate, and stable than techniques with a polychromatic IR source (i.e., large band of wavelengths) because selection of the absorption of a specific wavelength from a polychromatic IR source is difficult to achieve.
One main advantage of optical techniques is that they make monitoring of concentration dynamics in near real time possible, including monitoring several gases with different concentrations at the same time (Powers and Capelari, 2016). Advantages of optical instruments include linear responses over a wide range of concentrations and the ability to measure concentrations both inside (where there could be a high concentration level) and outside (low concentration level) the animal house with the same instruments. Most optical instruments have response times adapted to measurement in animal houses. They are portable and can be used on site. Nevertheless, they can be expensive, must be calibrated, and still require accurate estimation of ventilation rate.
Gas Chromatography
A gas chromatograph separates components in the sample and measures their concentrations. The equipment has four basic elements: an injector, a column, an oven surrounding the column, and a detector. The sample is vaporized in the injector and swept by the carrier gas through a heated column. The column separates each compound according to its polarity and boiling point. The detector identifies and quantifies the compounds separated. The detectors include a flame ionization detector for CH 4 and CO 2 and an electron capture detector for N 2 O. This technique is accurate if the detector has been calibrated for the range of concentrations measured. It requires use of a carrier gas and regular calibration, which makes on-site implementation and continuous measurement difficult. It is often used to measure previously collected samples.
Chemiluminescence
Chemiluminescence is used to measure NH 3 concentration. NH 3 in the sample is first oxidized to N 2 O by a catalytic converter, and then the N 2 O is further oxidized to nitric oxide (NO) at high temperature and an elevated energy state. As the molecules return to a lower energy state, they release electromagnetic radiation at a specific wavelength, which is measured and quantified.
Acid Traps
An acid trap is a standard reference technique for measuring NH 3 . A known volume of air is pumped through an acid solution and recorded (Figure 4.5.6). The acid solution is later analyzed in the laboratory with a colorimetric or photometric method (Hassouna et al., 2016) to estimate the amount of NH 3 trapped in the solution, as:
\[ NH_{3,trapped} = [N-NH_{4}^{+}]_{acid\ solution} \times m_{acid\ solution} \]
where NH 3 , trapped = amount of NH 3 trapped in the solution (kg)
[ N-NH 4 + ] acid solution = concentration of ammonium in the acid solution (kg kg −1 )
m acid solution = mass of the solution (kg)
From this, NH 3 concentration in the air sample (\(C_{N-NH_{3}, air}\) in kg m −3 ) can be calculated as:
\[ C_{N-NH_{3, air}} = \frac{NH_{3, trapped}}{V_{sample}} \]
where V sample (m 3 ) is the volume of air that passed through the solution.
Strong acid solutions are used, such as boric acid, orthophosphoric acid, nitric acid, and sulfuric acid. The trap can be used for a few hours or a few days depending on the NH 3 concentrations in the incoming air, the acid concentration, and volume of acid solution in the vials. Sampling time and concentration should be determined before the experiment as a function of the expected NH 3 concentrations. Two vials with acid solution are used sequentially to avoid saturating a single solution. This technique provides a mean NH 3 concentration over the sampling period and thus is not suitable for studies that require monitoring dynamics of NH 3 concentrations in a house. Nevertheless, as it is not expensive or too time-consuming, it can be used to check the consistency of measurements made, for instance, with optical techniques.
Active Colorimetric Tubes
Active colorimetric tubes are a manual technique that can be used to estimate NH 3 , NO, volatile organic compounds (VOC), and CO 2 concentrations. Tubes are manufactured to react to a specific range of concentrations of a specific target gas. Before measurement, both ends of a sealed test tube are cut open. The tube is connected tightly to a hand pump, which draws air through the tube. If present in the air, the target gas reacts with reagents in the tube. The strength of the reaction is proportional to the concentration of the gas in the air. A graduated scale is used to read the degree of color change in the tube, which indicates the concentration of the target gas. Many of the reactions used are based on pH indicators, such as bromophenol blue to measure NH 3 concentrations. Gas concentration is expressed in ppm or mL m −3 . This technique is reliable and simple to use. It can be used to estimate concentrations, but not to measure them continuously or accurately.
Ventilation Rate
In mechanically ventilated houses with modern ventilation control systems, ventilation rate could be one of many data recorded continuously. In such situations, the data are thus easily available for emission calculations. For other houses, or if the time step of recording is not suitable or recorded data are not reliable, the ventilation rate must be measured or assessed. Different methods to estimate the ventilation rate have been evaluated and described in the literature (Ogink et al., 2013; Wang et al., 2016). The method chosen depends on the type of ventilation (natural or mechanical), the accessibility of the exhaust to make physical measurements, the level of ventilation rate, and the desired degree of accuracy. Some techniques are indirect (tracer gas, heat balance), while others are direct (fan wheel anemometer, specialized instruments).
Tracer Gas Techniques Using Artificial Tracer Gases
Tracer gas techniques are commonly used to quantify the ventilation rate in many kinds of houses, but mainly those with natural ventilation. An external tracer gas should be safe, inert, measurable, not produced in the house, and inexpensive (Phillips et al., 2001; Sherman, 1990). The most common tracer gas used in animal houses is sulfur hexafluoride (SF 6 ) (Mohn et al., 2018). A critical requirement is that of near-perfect air mixing inside the animal house to ensure that the tracer gas and the targeted gas (for emission calculations) being measured both disperse in a similar way. Air can be mixed artificially using a purpose-built ventilation duct (Figure 4.5.7). Tracer gases can be dosed automatically using a mass flow controller and critical orifices (Figure 4.5.8).
The basic principle for tracer gas techniques is conservation of mass (of both target gas and tracer gas). By monitoring the dosed mass flow and concentration at the sampling points of the tracer gas, the ventilation rate can be determined (Figure 4.5.9). A tracer gas release technique is chosen based on the ventilation rate, the detection limit of the device used to monitor tracer gas concentration, and the ability to control and monitor the dosed mass flow accurately. According to Ogink et al. (2013), three tracer gas release techniques can be distinguished:
- • constant injection method: tracer gas is injected at a constant rate, and its concentration is measured directly over a period of time and used to estimate the ventilation rate;
- • decay method: tracer gas is injected until its concentration stabilizes, then injection is stopped and the decay in concentration is used to calculate the ventilation rate; and
(a)
(b)
Figure \(\PageIndex{8}\): (a) Tracer-gas dosing by steel tubes with critical orifices protected by steel elements next to the floors in a dairy housing; (b) gas bottles with mass-flow controller.
- • concentration method: tracer gas is distributed in the air of a house to a certain concentration to be constant.
Only the constant injection method and the decay method are common for measurements in animal houses.
To calculate the emission or mass flow of the target gas (e.g., NH 3 , CH 4 ), a background correction of the concentration ( C x ) must first be calculated for the target gases and the tracer gases:
\[ C_{x} = C_{x, id} - C_{x, bgd} \]
where x = T (tracer gas) or G (target gas)
C x,id = indoor gas concentration (μg m −3 )
C x,bgd = background gas concentration (μg m −3 )
The ratio of the background concentrations of emitted (target) gas, C G , and tracer gas, C T , then corresponds to the ratio of their mass flow rates (\(\dot{m}\), g d −1 ):
\[ \frac{\dot{m}_{G}}{\dot{m}_{T}} = \frac{C_{G}}{C_{T}} \]
and thus
\[ \dot{m}_{G} = \frac{\dot{m}_{T}C_{G}}{C_{T}} \]
Carbon Dioxide (CO 2 ) Mass Balance or Tracer Gas Methods Using an Internal Tracer
The CO 2 mass balance method is sometimes considered a tracer gas technique in which CO 2 is used as an internal tracer, that is, not dosed but produced by animal respiration and manure. It can be used in naturally or mechanically ventilated houses. It is based on the hypothesis that ventilation rate determines the relationship between CO 2 production in the house and the difference in CO 2 concentrations between the inside and outside of the house. This method has been widely described (Blanes and Pedersen, 2005; Estellés et al., 2011; Samer et al., 2012) and is more accurate in buildings with no litter and no gas heating system.
The ventilation rate for the house can be calculated as:
\[ VR = \frac{\text{total heat per house}\times \text{ventilation flow per hpu}}{1000} \]
where the total heat produced for the entire house is expressed in heat production units (hpu; 1 hpu is 1 kW of total animal metabolic heat production at 20°C) and the ventilation flow per hpu is in m 3 h −1 hpu −1 .
The International Commission of Agricultural Engineering provides a method to calculate total heat production (sensible plus latent) for different animal categories (Pedersen and Sällvik, 2002). For instance, for fattening pigs, the total heat produced for the entire house is calculated by multiplying the total heat per animal (in W animal −1 ) by the number of animals and converting to heat production units as:
\[ \text{total heat per house} = \text{total heat per animal} \times \text{number of animals} \]
\[ \text{total heat per animal} = (5.09\times m^{0.75} +[1-(0.47+0.003 \times m)] \times [(n \times 5.09 \times m^{0.75}) - (5.09\times m^{0.75})] \]
where m = animal mass (kg)
n = feed energy in relation to the heat dissipation due to maintenance (g d −1 )
Ventilation flow per hpu varies as a function of animal activity at different times of the day and difference between indoor and outdoor CO 2 concentrations:
\[ \text{Ventilation flow per hpu} = \frac{c \times (\text{relative animal activity})}{(CO_{2,indoors}-CO_{2,outdoors})\times 10^{-6}} \]
where c = CO 2 production (m 3 h −1 hpu −1 ); varies as a function of animal type (Pedersen and Sällvik, 2002; Pedersen et al., 2008).
\( CO_{2, indoors} \text{ and } CO_{2, outdoors} = \text{measured indoor and outdoor } CO_{2} \text{ concentrations at time h (mL m}^{-3}) \)
Relative animal activity is calculated as:
\[ \text{Relative animal activity} = 1-a\ sin[(\frac{2\pi}{24} \times (h+6-h_{min})] \]
where a = constant expressing amplitude with respect to the constant value 1, which is a scaling factor based on empirical observation and which varies depending on the animal type (Pedersen et al., 2008)
h = time at sampling (this should be a decimal number 0 ≤ h ≤ 24), e.g., (2:10 = 2.2)
h min = activity factor that relates to the time of day with minimum activity (hours after midnight) (Pedersen and Sällvik, 2002)
Use of Sensors
Fan wheel or hot wire anemometers can be used to quantify ventilation rate in mechanically ventilated houses that draw outlet air through ducts or exhaust fans. One important requirement is having access to exhaust flow where the measurements are to be made, which is not possible in many animal houses.
The anemometer measures air velocity, and ventilation rate ( VR ) is calculated as follows:
\[ VR=sA \]
where s = mean airspeed (m h −1 )
A = cross-sectional area of the ventilation duct or air stream (m 2 )
Proper methods must be utilized to obtain representative mean air velocity over the flow area, for example by selecting a sufficient number of measurement points and applying either log-linear or log-Tchebycheff rules (ISO 3966, 2008) for measurement points spacing.
Use of anemometers is not recommended in naturally ventilated houses because of their rapid change in air fluxes and large size of the open area, which would require many sensors to obtain a representative estimate of the ventilation rate.
In mechanically ventilated houses, continuous monitoring of the static pressure differential and the operating status (on-off) of each fan can be used to estimate the fan’s ventilation rate based on its theoretical or measured performance characteristics. Ideally, the in situ performance of each fan is determined first, and the house ventilation rate can be estimated by summing all operating fan flow rates. For example, Gates et al. (2004, 2005) developed and improved a fan assessment numeration system (FANS) to measure the in situ performance curve of ventilation fans operating in a negative pressure mechanically ventilated animal house (Figure 4.5.10). This unit is placed either against a fan on the inside of the house, or at the fan exterior with appropriate flexible ducting (Morello et al., 2014) to direct all airflow through the unit. A series of anemometers traverse the entire flow area to obtain a single mean air velocity, which is multiplied by the calibrated unit cross sectional area. A series of these measurements taken at different building static pressures provides an empirical fan performance curve, obtained, for example, from the regression equation of measured flow on building static pressure. Then, measurements of fan run-time and concurrent static pressure can be used to determine reasonably accurate airflow rates for each fan, and their sum is the building ventilation rate. Previous work has clearly shown that neglecting to account for building ventilation by means of direct measurement results in substantial loss in accuracy of estimates for ER , due to the variation among fans.
The Mass Balance Approach for a Global Estimation of N and C Emissions and Emissions Measurement Validation
A mass balance approach estimates emissions based on changes in livestock over time, without the need to measure emissions directly (Figure 4.5.11). The approach estimates total N or C emissions rather than emissions of specific gases (e.g., N-NH 3 , N-N 2 O, N 2 , C-CH 4 , C-CO 2 ) or emission dynamics. The accuracy of mass balance calculations depends on the technical and livestock management data available, characterization of the manure and feed, and, in certain cases, the length of the period considered. To test the validity of the data used to calculate an N or C mass balance, those of non-volatile elements such as phosphorus (P) and potassium (K) must be calculated. As the latter elements are non-volatile, their mass balance deficits (difference between inputs and outputs) should be zero, but the data used in calculations will have uncertainty, especially under commercial conditions. If the mass balance deficit for P and K is too high (e.g., > 15%), then the estimates of total N and C emissions must be reconsidered.
The estimation of N, C, or water emissions ( X emissions, where X is for N, C, or water) over the production period can be calculated according to the following equation:
\[ X_{inputs}-X_{outputs} = X_{emissions} \]
X inputs and X outputs are the quantity of X in all inputs and outputs. The estimation of these quantities requires careful data collection (quantities, chemical compositions) concerning animals, feed, eggs or milk (a function of animal production), litter, manure, and animal mortality. Models should be used to estimate the quantity of X in animals as a function of their weight.
Applications
Implementing the different emissions measurement methods in an animal house requires the development of a protocol based on the objectives of the project, the specifics of the animal house, the interior environment, and outdoor weather. Three important points that should be considered in a protocol concern the sampling, the data acquisition, and the validity check of the measurements.
Sampling and Sensor Locations
Evaluation of gas emissions requires measurement of inlet and outlet gas concentration. Sampling at air inlets or outlets is recommended if they can be identified, if their locations are fixed over the measurement period, and if they can be easily reached. When these conditions cannot be fulfilled, multiple locations inside the house are usually selected to provide a mean indoor concentration to accommodate spatial variability of indoor concentration. The same should be done for outdoor concentration.
The presence of animals inside the animal area makes installation of gas sensors or sampling tubes more complicated. Ideally, they should be installed when no animals are in the house, such as during an outdoor or vacancy period. They should be located where animals cannot bite, bump, or move them, and should be carefully protected from animals (Figure 4.5.12). Successful sensor placement requires a trade-off between minimizing animal disturbance and maximizing the representativeness of measurements.
The environment inside animal housing is generally harsh for sensors and the air sampling system. Direct exposure to the combination of humidity, NH 3 , and suspended particulate matter can damage the sensors (Figure 4.5.13). Furthermore, indoor air is generally warmer and more humid than outdoor air because of animal heat production or the use of a heating or cooling system inside the house. These differences should be considered when sampling indoor air; for example, sampling tubes should be heated and insulated if air samples are analyzed in a cooler place and condensation within sampling lines might be expected.
Data Acquisition
During the production period, emissions can vary greatly during a 24-hour cycle and over longer time intervals. Variability is due to the same parameters that affect spatial variability, changes in animal behavior, their excretion patterns and quantity, and whether or not they have outdoor access. For instance, fattening pigs and poultry will excrete more total ammonia nitrogen (TAN) each day as they grow, yielding ever higher potential for NH 3 emissions. These two kinds of temporal dynamics (daily and production period) must be considered when measuring gas emissions.
Information concerning the production conditions (number of animals, feed and water consumption, animal mortality) and outdoor climate are also required for validation of measurements and comparison with emissions data already published. All operations made by the farmers or operators (for instance, feeding changes, litter supply, or cooling system implementation) and specific events (for instance, electric power shutdown) during the measurement period should be noted because they will be helpful for data analysis and interpretation.
Validation of Measurements
In order to achieve good quality measurements, data validation steps are necessary at several levels:
- • Validation measurements for parts or the whole measuring setup should be carried out in advance, especially if the setup, single components, and/or the measurement objective (e.g., housing system) was not measured in this configuration before.
- • Calibration of analytical devices and sensors has to be performed according to their specifications. For some analytical instruments, measurements with a reference method (e.g., acid traps for NH 3 ) are recommended.
- • Frequent checks of operational mode and measurement values as well as housing and management conditions are necessary.
- • Plausibility checks of raw data and emission values (e.g., comparison of courses of gas concentrations and wind speed, data check in view of a predetermined plausible range based upon user scientific and technological knowledge) help to find outliers, non-logical values, etc. These incorrect values have to be eliminated according to predefined criteria.
- • Redundancy in measurements can enhance the reliability of the values. For instance, CO 2 concentrations could be measured with both a gas chromatograph and an optical gas analyzer during startup or periodically over the project.
- • Comparison of the cumulative emissions for N and carbon (C) with N and C mass balance deficits over the measuring period.
Examples
Example \(\PageIndex{1}\)
Example 1: Calculate ammonia (NH 3 ) emission rate from a mechanically ventilated pig house using the carbon dioxide mass balance approach
Problem:
The following case study is based on a project undertaken on behalf of the Irish Environmental Protection Agency to test the suitability of existing NH 3 emission factors currently being used for different pig life stages and to explore the potential impact on Natura 2000 sites (i.e., Special Areas of Conservation and Special Protection Areas that may be sensitive to N). The monitoring equipment is described in detail by Kelleghan et al. (2016).
The house used mechanical ventilation, with air inlets along the side of the house and ceiling exhaust fans, but no access to the exhaust stream for direct measurement of ventilation rate. Gas concentrations were measured at 10 a.m. in a house with 406 fattening pigs of 81.25 kg animal −1 reared on a fully slatted floor. Indoor NH 3 concentrations in the house were measured using a Los Gatos Research ultraportable ammonia analyzer (UAA) in combination with an eight-inlet multiport unit allowing for multiple sampling points. Outdoor concentrations were not measured; for the purposes of this study and the calculations, they were assumed to be zero. Indoor and outdoor CO 2 was measured in the sample gas drawn by the UAA using a K30 CO 2 sensor (Senseair, Sweden). Measured gas concentrations are presented in Table 4.5.1. Additional parameters adapted for finishing pigs are included in Table 4.5.2. Calculate the building ventilation rate and the NH 3 emission rate.
Solution
Calculate the building ventilation rate using the CO 2 mass balance approach expressed by Equation 4.5.6:
| Measured | |
|---|---|
|
CO 2,indoors |
915 ppm (mL m −3 ) |
|
CO 2,outdoors |
403 ppm (mL m −3 ) |
|
NH 3,indoors |
3.73 (mg m 3 ) |
|
NH 3,outdoors |
0 (mg m 3 ) |
\( VR=\frac{\text{total heat per house} \times \text{ventilation flow per hpu}}{1000} \) (Equation \(\PageIndex{6}\))
To calculate the total heat per house, first, calculate the relative animal activity with Equation 4.5.10 using the given values:
| Parameter | Value for This Experiment |
|---|---|
|
a (Equation 4.5.11) |
0.53 |
|
h min (Equation 4.5.11) |
1:40 AM = 1.7 in equation |
|
n (Equation 4.5.9) |
3.38 (g day −1 ) |
|
c (Equation 4.5.10) |
m 3 h −1 hpu −1 |
\( \text{Relative animal activity} = 1-a\ sin[(\frac{2\pi}{24})\times(h+6-h_{min})] \) (Equation \(\PageIndex{10}\))
\( \text{Relative animal activity} = 1-0.53\times sin[(\frac{2\pi}{24})\times(10+6-1.7)] = 1.2994 \)
Next, calculate the total heat production per animal with Equation 4.5.8:
\( \text{Total heat per animal} = 5.09 \times m^{0.75} + [1-(0.47+0.003\times m)]\times [(n \times 5.09\times m^{0.75})-(5.09\times m^{0.75})] \) (Equation \(\PageIndex{8}\))
\( \text{Total heat per animal} = 5.09 \times 81.25^{0.75} + [1-(0.47+0.003\times 81.25)]\times [(0.00338 \times 5.09\times 81.25^{0.75})-(5.09\times 81.25^{0.75})] = 231.6\ W \text{ animal}^{-1} \)
Thus, with 406 pigs, the total heat production for the house is:
\( 406 \times 231.6 = 94026.5\ W \)
Next, calculate ventilation flow per heat producing unit (hpu) with Equation 4.5.9:
\( \text{Ventilation flow per hpu} = \frac{c \times (\text{relative animal activity})}{CO_{2,indoors}-CO_{2,outdoors} \times 10^{-6}} \) (Equation \(\PageIndex{9}\))
\( \text{Ventilation flow per hpu} = \frac{0.185 \times (1.2994)}{(915-403) \times 10^{-6}} = 469.5 \)
Ventilation flow per hpu will equal 469.5 m 3 h −1 hpu −1 .
Finally, substitute the computed values into Equation 4.5.6 to calculate the building ventilation rate:
\( VR = \frac{\text{total heat per house} \times \text{ventilation flow per hpu}}{1000} \) (Equation \(\PageIndex{6}\))
\( VR = \frac{94026.5 \times 469.5}{1000} = 44,145.2 \)
The building ventilation rate is 44145.2 m 3 h −1 .
To calculate NH 3 emission rate, note that the NH 3 emission rate for the house is proportional to the difference between indoor and outdoor NH 3 concentrations multiplied by the ventilation rate:
\( \frac{(3.73-0)\times 44,145.2}{3600} = 45.7 \)
The NH 3 emission rate for this example is 45.7 mL s −1 . This equates to 9.7 g day −1 animal −1 .
Example \(\PageIndex{2}\)
Example 2: Calculate methane (CH 4 ) emissions from a naturally ventilated dairy cattle house using tracer gas (SF 6 ) measurement data
Problem:
This example is based on investigations carried out in experimental dairy housing for emission measurements (Mohn et al., 2018). The housing consists of two experimental compartments, each for 20 dairy cows, and a central section for milking, technical installations, an office, and analytics. The experimental compartments are naturally ventilated without thermal insulation and with flexible curtains as facades.
The diluted tracer gas, SF 6 , was dosed continuously through steel tubes with critical capillaries (every third meter) next to the aisles to mimic the emission sources. Stainless steel tubes and critical orifices were protected with metal profiles from damage by animals and contamination with excrement. To adjust analyzed tracer gas concentration in an optimal range (> 0.05 μg m −3 , < 1.5 μg m −3 SF 6 ), tracer gas flow was set according to meteorological and ventilation conditions (e.g., curtains open/closed) by mass flow controllers. Integrative air samples at a height of 2.5 m with a piping system consisting of Teflon tubes and critical glass orifices (every second meter) allow a representative sample. Teflon filters protected the critical orifices from dust and insects. Flow rates for individual orifices of the dosing and sampling systems were monitored before and after every measuring period using mass flow meters. The analytical instrumentation for CH 4 (cavity ring-down spectrometer, CRDS, Picarro Inc., Santa Clara, CA, USA) and SF 6 analysis (GC-ECD, Agilent, Santa Clara, CA, USA) was located in an air-conditioned trailer in the central section. The two compartments were sampled alternately for 10 min. each. Further, once per hour, the background (approximately 25 m from housing, unaffected by the housing) was sampled, so at least two 10-min samples per compartment were obtained every hour.
To describe the measurement situation, relevant accompanying parameters such as housing and outdoor climate, animal parameters (e.g., live weight, milk yield, milk composition, milk urea content, urine urea content), and feed (quality and quantity, amount of trough residue) were recorded.
Calculate the CH 4 emissions during one 10-min measurement taken on 23 September at 12:40 p.m. in a compartment with perforated floors holding 20 cows. The measured gas concentrations are presented in Table 4.5.3.
Solution
Calculate the background correction ( C x ) according to Equation 4.5.3 using measured concentrations of SF 6 \((C_{SF6})\) and CH 4 \((C_{CH4})\):
| Parameter | Value |
|---|---|
|
SF 6 mass flow |
2.879 g d −1 |
|
SF 6 background |
0.052 μg m −3 |
|
SF 6 housing, sampling points |
1.820 μg m −3 |
|
CH 4 background |
1384.2 μg m −3 |
|
CH 4 housing, sampling points |
9118.6 μg m −3 |
\( C_{x}=C_{x,sp}-C_{x,bgd} \) (Equation \(\PageIndex{3}\))
\( C_{CH4}=9118.6-1384.2=7734.4\ \mu g \ m^{-3} \)
\( C_{SF6}=1.820-0.052=1.768\ \mu g \ m^{-3} \)
Calculate emission or mass flow calculation of CH 4 using Equation 4.5.5:
\( \dot{m}_{G} = \frac{\dot{m}_{T} \times C_{G}}{C_{T}} \) (Equation \(\PageIndex{5}\))
\( \dot{m}_{CH4} = \frac{2.879\ g \ d^{-1} \times 7734.4\ \mu g\ m^{-3}}{1.768\ \mu g\ m^{-3}} = 12,597.9\ g\ d^{-1} \)
ER per cow (20 cows per compartment): 629.7 g d −1
Image Credits
Figure 1. Department for Environment Food & Rural Affairs. (CC By 4.0). (2018). Environmental impacts of ammonia emissions. Retrieved from https://www.gov.uk/government/publications/code-of-good-agricultural-practice-for-reducing-ammonia-emissions/code-of-good-agricultural-practice-cogap-for-reducing-ammonia-emissions
Figure 2. Calvet, S. (CC By 4.0). (2014). Process leading to ammonia emission and contributing factors. Adapted from Snoek et al.
Figure 3. Calvet, S. (CC By 4.0). (2001). Reactions leading to N2O emissions: nitrification (in green) and denitrification (in blue). Adapted from Wrage et al.
Figure 4. Calvet, S. (CC By 4.0). (2020). Process and microorganisms involved in methane formation.
Figure 5. Calvet, S. (CC By 4.0). (2020). Direct emission measurement in an animal house. The difference in concentration between indoors and outdoors and the ventilation rate must be measured (adapted from Calvet et al., 2013).
Figure 6. Hassouna, M. (CC By 4.0). (2020). Acid trap configuration.
Figure 7. Hassouna, M. (CC By 4.0). (2020). Duct for dispersing a tracer gas within an animal house.
Figure 8. Agroscope, Schrade, S. (CC By 4.0). (2020). (a) Tracer-gas dosing by steel tubes with critical orifices protected by steel elements next to the floors in a dairy housing; (b) gas bottles with mass-flow controller. Photos adapted from Agroscope. [Fair Use].
Figure 9. Agroscope, Schrade, S. (CC By 4.0). (2020). Principle of the tracer gas method.
Figure 10. Gates, R. (CC By 4.0). (2020). Fan Assessment Numeration System (FANS) developed by Gates et al. (2005) to describe the performance curve of a ventilation fan in an animal house. Note the unit can be used on either the inlet or exhaust side of the ventilation fan.
Figure 11. Hassouna, M. (CC By 4.0). (2016). The mass balance approach in animal houses.
Figure 12. Right. Agroscope, Schrade, S. (CC By 4.0). (2020). Sensors must be installed beyond the reach of animals.
Figure 12 Left. Hassouna, M. (CC By 4.0). (2020). Sensors must be installed beyond the reach of animals.
Figure 13. Hassouna, M. (CC By 4.0). (2020). Clogging of a sampling tube and its dust filter after three months of measurement in a dairy cattle house.
References
Blanes, V., & Pedersen, S. (2005). Ventilation flow in pig houses measured and calculated by carbon dioxide, moisture and heat balance equations. Biosyst. Eng. , 92 (4), 483-493. https://doi.org/10.1016/j.biosystemseng.2005.09.002 .
Calvet, S., Gates, R. S., Zhang, G., Estelles, F., Ogink, N. W. M., Pedersen, S., & Berckmans, D. (2013). Measuring gas emissions from livestock buildings: A review on uncertainty analysis and error sources. Biosyst. Eng. , 116 (3), 221-231. https://doi.org/10.1016/j.biosystemseng.2012.11.004 .
Estelles, F., Fernandez, N., Torres, A. G., & Calvet, S. (2011). Use of CO 2 balances to determine ventilation rates in a fattening rabbit house. Spanish J. Agric. Res. , 9 (3), 8. doi.org/10.5424/sjar/20110903-368-10.
Gates, R. S., Casey, K. D., Xin, H., Wheeler, E. F., & Simmons, J. D. (2004). Fan assessment numeration system (FANS) design and calibration specifications. Trans. ASAE , 47 (5), 1709-1715. https://doi.org/10.13031/2013.17613 .
Gates, R. S., Xin, H., Casey, K. D., Liang, Y., & Wheeler, E. F. (2005). Method for measuring ammonia emissions from poultry houses. J. Appl. Poultry Res. , 14 (3), 622-634. https://doi.org/10.1093/japr/14.3.622 .
Hassouna, M., Eglin, T., Cellier, P., Colomb, V., Cohan, J.-P., Decuq, C., . . . Ponchant, P. (2016). Measuring emissions from livestock farming: Greenhouse gases, ammonia and nitrogen oxides. France: INRA-ADEME.
ISO 3966. (2008). Measurement of fluid flow in closed conduits. Velocity area method for regular flows using Pitot static tubes.
Kelleghan, D. B., Hayes, E. T., & Curran, T. P. (2016). Profile of ammonia and water vapor in an Irish broiler production house. ASABE Paper No. 162461252. St. Joseph, MI: ASABE. https://doi.org/10.13031/aim.20162461252 .
Mohn, J., Zeyer, K., Keck, M., Keller, M., Zahner, M., Poteko, J., . . . Schrade, S. (2018). A dual tracer ratio method for comparative emission measurements in an experimental dairy housing. Atmospheric Environ. , 179 , 12-22. https://doi.org/10.1016/j.atmosenv.2018.01.057 .
Morello, G. M., Overhults, D. G., Day, G. B., Gates, R. S., Lopes, I. M., & Earnest Jr., J. (2014). Using the fan assessment numeration system (FANS) in situ: A procedure for minimizing errors during fan tests. Trans. ASABE , 57 (1), 199-209. https://doi.org/10.13031/trans.57.10190 .
Ogink, N. W. M., Mosquera, J., Calvet, S., & Zhang, G. (2013). Methods for measuring gas emissions from naturally ventilated livestock buildings: Developments over the last decade and perspectives for improvement. Biosyst. Eng. , 116 (3), 297-308. https://doi.org/10.1016/j.biosystemseng.2012.10.005 .
Pedersen, S., & Sallvik, K. (2002). 4th Report of working group on climatization of animal houses. Heat and moisture production at animal and house levels. Research Centre Bygholm, Danish Institute of Agricultural Sciences.
Pedersen, S., Blanes-Vidal, V., Jorgensen, H., Chwalibog, A., Haeussermann, A., Heetkamp, M. J., & Aarnink, A. J. (2008). Carbon dioxide production in animal houses: A literature review. Agric. Eng. Int.: CIGR J.
Phillips, V. R., Lee, D. S., Scholtens, R., Garland, J. A., & Sneath, R. W. (2001). A review of methods for measuring emission rates of ammonia from livestock buildings and slurry or manure stores, Part 2: Monitoring flux rates, concentrations and airflow rates. J. Agric. Eng. Res. , 78 (1), 1-14. https://doi.org/10.1006/jaer.2000.0618 .
Powers, W., & Capelari, M. (2016). Analytical methods for quantifying greenhouse gas flux in animal production systems. J. Animal Sci. , 94 (8), 3139-3146. https://doi.org/10.2527/jas.2015-0017 .
RAMIRAN. (2011). Glossary of terms on livestock and manure management. Retrieved from http://ramiran.uvlf.sk/doc11/RAMIRAN%20Glossary_2011.pdf .
Samer, M., Ammon, C., Loebsin, C., Fiedler, M., Berg, W., Sanftleben, P., & Brunsch, R. (2012). Moisture balance and tracer gas technique for ventilation rates measurement and greenhouse gases and ammonia emissions quantification in naturally ventilated buildings. Building Environ. , 50 , 10-20. https://doi.org/10.1016/j.buildenv.2011.10.008 .
Sherman, M. H. (1990). Tracer-gas techniques for measuring ventilation in a single zone. Building Environ. , 25 (4), 365-374. https://doi.org/10.1016/0360-1323(90)90010-O .
Snoek, D. J. W., Stigter, J. D., Ogink, N. W. M., & Groot Koerkamp, P. W. G. (2014). Sensitivity analysis of mechanistic models for estimating ammonia emission from dairy cow urine puddles. Biosyst. Eng. , 121 , 12-24. https://doi.org/10.1016/j.biosystemseng.2014.02.003 .
Wang, X., Ndegwa, P. M., Joo, H., Neerackal, G. M., Stockle, C. O., Liu, H., & Harrison, J. H. (2016). Indirect method versus direct method for measuring ventilation rates in naturally ventilated dairy houses. Biosyst. Eng. , 144 , 13-25. https://doi.org/10.1016/j.biosystemseng.2016.01.010 .
Wrage, N., Velthof, G. L., van Beusichem, M. L., & Oenema, O. (2001). Role of nitrifier denitrification in the production of nitrous oxide. Soil Biol. Biochem. , 33 (12), 1723-1732. https://doi.org/10.1016/S0038-0717(01)00096-7 .


9.2: Causal Reasoning
We make causal judgments all the time. We think that the world is full of things causing other things to happen. He made me do it. The woman lost the race because she was anemic. The frog jumped off the leaf, causing it to shake and shower dew drops onto the ground below. You’re only cheating on this test because if you fail it, then you’ll have to drop out of college (don’t cheat, students, even if you are failing a course :) ). Roasting meat until it is charred and black causes cancer.
How, though, do we know that there’s a causal connection between two factors or events or things? We have to go through a particular process to demonstrate it. It’s sort of a more specific version of the hypothetical method we discussed above.
First , we establish that there is in fact a correlation between two things. There’s a correlation between alcohol use and liver disease. As one drinks more alcohol more regularly, one’s chances of developing liver disease increase proportionately.
Correlation, though, is cheap. There is a hilarious website called Spurious Correlations with a collection of graphs demonstrating the odd things that are correlated with one another. Check it out! It turns out Nick Cage films correlate quite closely with deaths by drowning in a pool. Per capita mozzarella consumption correlates with civil engineering doctorate awards. So we need to get beyond mere correlation in order to posit a causal connection. We need to give an account and run some tests.
Second , we need to develop a causal story or an account of how they actually might be correlated. The more doctorate awards are presented, the more wine and cheese receptions there are and the more wine and cheese receptions there are, the more mozzarella cheese is consumed. Plausible? Meh, not really. But that would be how we would fill in the gap between the two factors.
Gamma radiation exposure causes cancer. We know it is highly correlated, but beyond that, we actually have a story of how it causes cancer. Gamma radiation mutates cellular DNA, which either activates or creates genes which code for uncontrolled growth. That’s more or less the story of how gamma radiation and cancer are causally linked. We need this story because we need to understand how it possibly could be that gamma radiation has a causal effect on cancer.
Finally , we need to do perhaps the most important step: we need to test our hypothesis. We need to establish that the more radiation one is exposed to, the more likely one is to have cancer . Or if there were no civil engineering doctoral degrees awarded, then no one would consume mozzarella that year . We need to actually manipulate the variables involved until we have satisfied ourselves that by manipulating the cause we can manipulate the effect. For example, by removing the gamma exposure, we should dramatically decrease someone’s chances of developing cancer.
1. Establish a prima facie correlation
2. Develop a causal theory or story or account
3. Test for concomitant variation
If we’ve only established a correlation between two variables or factors and then came up with a story about how they might share a causal connection, then we’ve stopped short of truly knowing that there is a causal connection between the two. We have to intervene between the two factors to be sure that one truly causes the other. Otherwise the cause might be something that we haven’t yet thought of.


7.8: Protein misfolding and denaturation
- Understand misfolding of proteins and the medical problems associated with it.
- Understand the denaturation of proteins and what causes the denaturation.
Protein misfolding and associated diseases
Newly synthesized proteins fold in a specific way, i.e., into secondary, tertiary, and quaternary structures, to be able to perform their function, as illustrated in Figure \(\PageIndex{1}\). Some proteins can fold in only one way, but others can fold in multiple ways. There are proteins in the cell, called chaperones, that help newly formed proteins to fold in the way needed for their function.
Sometimes normal proteins misfold and become pathological. Often, these proteins are in soluble \(\alpha\) helix forms that re-assembles into \(\beta\)-pleated sheet forms that are sticky and aggregate into plaques or amyloid structures, as illustrated in Figure \(\PageIndex{2}\), with the example of plaque formation in Alzheimer's affected brain.
Prions are small proteins found in nerve tissue. Their exact functions are unknown, but when they misfold, they can cause more normal proteins to misfold. This protein misfolding is related to diseases such as mad cow disease in cows, Creutzfeldt–Jakob disease in humans, Alzheimer's disease, and familial amyloid cardiomyopathy or polyneuropathy, as well as intracellular aggregation diseases such as Huntington's and Parkinson's disease.
Denaturation of proteins
Proteins usually keep their primary, secondary, tertiary, and quaternary structures under physiological conditions. However, some physical processes and chemical agents can beak the interactions, i.e., hydrogen bonding, disulfide linkages, salt bridges, and hydrophobic interactions.
Loss of the secondary, tertiary, and quaternary structures of proteins by a physical process or a chemical agent while maintaining the primary structure almost intact is called denaturation of proteins .
Proteins unfold and become almost linear polypeptide chains upon denaturation. Denatured proteins can not perform their functions. Denaturation can be caused by heat, acids or bases, organic compounds and solvents, heavy metal ions, and agitation, as explained below.
- Heating above 50 o C disrupts hydrogen bonding and hydrophobic interactions, causing protein denaturation. For example, cooking food and sterilizing surgical instruments by autoclave treatment. In laser surgery, laser, i.e., the light of a single wavelength, is focused on a spot, causing heat that denatures proteins. Heating by laser cauterizes incisions, i.e., burns the site or the wound. It helps prevent blood loss.
- Acids and bases disrupt hydrogen bonding and salt bridges, e.g., by neutralizing some ions involved in the salt bridges.
- Organic compounds like urea disrupt hydrogen bonding by replacing them with stronger hydrogen bonding with the compound, and organic solvents disrupt hydrogen bonding and hydrophobic interactions. For example, 75% alcohol sterilizes skin by denaturing and coagulating proteins.
- Heavy metals ions like \(\ce{Pb^{2+}}\) and \(\ce{Hg^{2+}}\) attack \(\ce{-SH}\) groups making salt bridges, like \(\ce{-S^{-}Pb^{2+} ^{-}S{-}}\). Egg white or milk is an antidote to heavy metal poisoning as they precipitate the metal ions in the stomach, based on the salt bridge forming reaction. Vomiting is induced to remove the metal before the precipitate is dissolved, releasing the metal in the later parts of the digestive system.
- Agitation physically disrupts hydrogen bonding and hydrophobic interactions. Whipped cream and whipped egg white are prepared based on the agitation process.


18.4: Annotated Sample Reading- "Celebrating a Win-Win" by Alexandra Dapolito Dunn
By the end of this section, you will be able to:
- Read a diverse range of texts in different genres to identify how conventions are shaped by purpose, language, culture, and audience expectation.
- Read effectively for inquiry, learning, critical thinking, and communication in various rhetorical and cultural contexts.
- Demonstrate the relationships between ideas, patterns of organization, and verbal and nonverbal elements.
Introduction
Figure \(18.12\) Alexandra Dapolito Dunn (credit: “Alex Dunn, assistant administrator at US EPA” by Eric Vance/ Wikimedia Commons, Public Domain)
As a multimodal composer, you may choose to employ ethos, a rhetorical method of persuasion. In this context, ethos is an appeal to readers in order to establish the author’s credibility and character. In a rhetorical appeal, you can use ethos through fair, neutral language to show trustworthiness. In multimodal composition, ethos aims to convince readers that you are a reliable and an ethical expert on the subject. When using ethos, authors present sources that support their argument in balanced and honest ways, revealing their writing to be reliable. Authors also seek to understand their audience, establishing commonalities between those who support the issue, those who are undecided or indifferent, and those who dissent. Often, authors invoke the words or ideas of respected figures, authorities, or even religious texts when using ethos to convince readers. Analyzing multimodal compositions can help you learn how to use rhetorical frames in the multimodal composing process. In the blog post you are about to read, the author uses ethos, along with structural aspects of multimodal texts, to establish herself as a trustworthy expert on the subject of pollution prevention. Studying the components of multimodal writing in this blog will help you understand how multimedia platforms utilize elements of text, media, and modes.
Living By Their Own Words
"Celebrating a Win-Win: 30 Years of Progress under the Pollution Prevention Act" by Alexandra Dapolito Dunn (b. 1967)
On this day in 1990, a new era was ushered in for Environmental Protection Agency (EPA) and the nation when the Pollution (P2) Act was signed into law. The act gave the agency new tools to join with states, tribes, and communities to prevent pollution before it happens. It also marked a shift in the paradigm of environmental protection, which had been mostly focused on end-of-pipe pollution control and clean-up strategies.
Headline and Tone. The linguistic headline immediately allows readers to know the author’s position on the subject, and its visual component of boldfaced text allows readers to understand that it’s important. Not only does it clearly preface the article by informing the reader of its topic (the Pollution Prevention Act), but it also presents the author’s positive attitude toward the subject through the words celebrating and win-win.
Context. Dunn contextualizes the Pollution Prevention Act, showing it as a positive national achievement that partnered the government with the people to prevent pollution.
Equally important, the P2 Act strengthened EPA’s role as an ally of American businesses, helping them save billions of dollars and improve operations. As EPA Administrator Andrew Wheeler has said, “It’s far better to prevent pollution from occurring than to go in after the fact and clean it up.”
Quotation from an Authority. This quotation from the EPA administrator supports Dunn’s assertion that the P2 Act is good for America. The quotation helps lend credibility to the author’s claim that the P2 Act has been a success over the past 30 years.
Purpose. Dunn’s purpose is to show how the P2 Act has been successful over time. Thus far, she has supported the claims that it has improved the environment and helped local governments and private businesses.
The P2 Act greatly expanded the opportunities for “source reduction” to reduce or prevent pollution at the source through cost-effective changes in production, operation, and raw materials use. These changes can reduce the amount of pollution entering a waste stream or the environment prior to recycling, treatment or disposal, and can offer industry substantial savings in reduced raw material, pollution control, pollution clean-up and liability costs.
Short Paragraphs. Dunn uses short, easily digestible paragraphs in her blog post. Short paragraphs are visually effective on a screen and ensure that the reader is not overwhelmed by text while helping the writer organize ideas.
Ethos. Dunn uses neutral, measured language to convince the reader that she is a reliable and ethical expert.
One of EPA’s first pollution prevention successes was with its 33/50 Program, a voluntary program under which companies committed to reduce their releases of 17 top priority chemicals 33 percent by 1992 and by 50 percent by 1995. Subsequent EPA programs built on the 33/50 and P2 model and are still working to reduce pollution across the country today including EPA’s WaterSense ( https://openstax.org/r/watersense ), Safer Choice ( https://openstax.org/r/safer_choice ), Environmentally Preferable Purchasing ( https://openstax.org/r/ environmentally), Green Chemistry ( https://openstax.org/r/green ), and our SmartWay Transport Partnership Program ( https://openstax.org/r/smartway ). President Trump acknowledged the effectiveness of these and other EPA programs in a 2018 Executive Order that directed federal agencies to use EPA’s P2 resources to meet their statutory sustainable purchasing requirements.
Hyperlinks. Hyperlinks are a functional tool and employ the visual mode to command the reader’s attention. Dunn uses hyperlinks to the EPA programs she names, establishing the agency as a source of pollution prevention efforts and, as a result, an expert on the issues covered in the blog post. In addition, she links to the presidential executive order, which establishes credibility.
The P2 Act also serves as an authority for collecting information from reporting facilities through the Toxics Release Inventory ( https://openstax.org/r/toxics ) (TRI) about their management of certain toxic chemicals, including source reduction approaches. Since this reporting began in 1991, we have learned that over 24,000 unique facilities have taken more than 450,000 actions to prevent pollution and reduce the amount of toxic chemicals entering the environment, such as spill and leak prevention measures, using safer chemicals, modifying industrial processes, and updating operating procedures.
Transition between Paragraphs. By using the word also, Dunn signals that she is shifting to another success the EPA has achieved in preventing pollution.
Statistics as Supporting Evidence. To support the impact of the P2 Act, Dunn uses statistics as evidence to show that the act has facilitated the prevention of pollution and toxic chemicals.
Perhaps the most impactful and collaborative program to grow out of the P2 Act is EPA’s P2 Grants Program. Since 1990, EPA has awarded more than 1,200 grants to state, tribal, non-profit, and university partners to work directly with U.S. businesses to develop and implement source reduction techniques. With the assistance from P2 grants, businesses have been able to save over $1.5 billion since 2011 while also reducing the use of hazardous materials by over 570 million pounds.
Supporting Evidence. Dunn provides evidence of the success of the P2 Act by showing how one program has helped local governments and private businesses save money.
As we celebrate the 30th anniversary of the Pollution Prevention Act today, I would like to thank all our state and local pollution prevention partners, as well as all the businesses that have joined with us to score a true win-win for the American people.
Audience. Although this blog is written on a public government website, Dunn shifts focus at the end to directly address businesses and local governments that have partnered with her or her organization.
You can access this post on the EPA blog ( https://openstax.org/r/win-win ).
Discussion Questions
- Why does Dunn choose to use neutral language rather than emotional appeals in this blog post?
- Why does Dunn focus on the impact of the P2 Act on businesses, particularly on how the act is financially beneficial to those organizations?
- How might this blog post differ if the intended audience were different?
- What is the effect of Dunn’s shift to addressing specific partners at the end of the post?
- In your opinion, does Dunn effectively establish herself as a trusted source? Why or why not?


3.4: Vocabulario. Los colores y algunos adjetivos
-
- Last updated
- Save as PDF
- Erica Brown, Alejandra Escudero, María Cristina Montoya, & Elizabeth Small
- SUNY Oneonta via OER SUNY
Objetivos
- Identify the color of things
Vocabulario: descripciones
amarillo
azul
verde
morado
anaranjado
rosado
blanco
negro
marrón
gris
azul oscuro
azul claro
claro ( clear or light )
oscuro ( dark )
colorido ( colorful )
descolorido ( colorless )
opaco ( dull, opaque )
Algunos adjetivos:
interesante ( interesting )
inteligente
importante
grande ( big )
amable ( nice )
feliz ( happy )
alegre ( joyful )
fácil ( easy )
difícil ( difficult )
paciente/ impaciente
idealista/realista
optimista/pesimista
sociable
egoísta ( selfish )
- Text Only
-
Los colores
- rojo ( red )
- amarillo ( yellow )
- azul ( blue )
- verde ( green )
- morado ( purple )
- anaranjado ( orange )
- rosado ( pink )
- blanco ( white )
- negro ( black )
- marrón ( brown )
- gris ( gray )
- azul oscuro ( dark blue )
- azul claro ( light blue )
- claro ( clear or light )
- oscuro ( dark )
- colorido ( colorful )
- descolorido ( colorless )
- opaco ( dull, opaque )
Algunos adjetivos:
- interesante ( interesting )
- inteligente ( intelligent )
- importante ( important )
- grande ( big )
- amable ( nice )
- feliz ( happy )
- alegre ( joyful )
- fácil ( easy )
- difícil ( difficult )
- paciente/ impaciente ( patient/impatient )
- idealista/realista ( idealistic/realistic )
- optimista/pesimista ( optimistic/pessimistic )
- sociable ( sociable )
- egoísta ( selfish )
Contributors and Attributions
- Biomuseo. Authored by : F Delventhal. Located at : https://commons.wikimedia.org/wiki/File:Biomuseo_(10229212235).jpg . License : CC BY: Attribution
- Colors. Provided by : COERLL, The University of Texas at Austin. Located at : http://laits.utexas.edu/spe/vid/beg03c.html . License : CC BY: Attribution
- Light coffee. Located at : https://pxhere.com/es/photo/1369512 . License : CC0: No Rights Reserved
- Dark coffee. Located at : https://www.publicdomainpictures.net/es/view-image.php?image=272289&picture=fondo-de-los-granos-de-cafe . License : CC0: No Rights Reserved
- Red bird. Authored by : David Dennis. Located at : https://www.flickr.com/photos/davidden/2210361882 . License : CC BY-SA: Attribution-ShareAlike
- Yellow Bird. Authored by : Rebecca Selah. Located at : https://www.flickr.com/photos/rebeccaselah/8177433579 . License : CC BY: Attribution
- Authored by: ReganE. Authored by : ReganE. Located at : https://pixabay.com/es/photos/azul-ave-aviar-2382238/ . License : Other . License Terms : Pixabay license
- Green Bird. Authored by : Roshan Kamath. Located at : https://www.pexels.com/photo/green-bird-1661179/ . License : Other . License Terms : Pexels License ( https://www.pexels.com/photo-license/ )
- Violet-backed Starling, Cinnyricinclus leucogaster. Authored by : Derek Keats. Located at : https://commons.wikimedia.org/wiki/File:Violet-backed_Starling,_Cinnyricinclus_leucogaster,_at_Pilanesberg_National_Park,_Northwest_Province,_South_Africa_(16436889535).jpg . License : CC BY: Attribution
- Orange bird. Located at : https://www.maxpixel.net/Orange-Bird-Animal-Parrot-Babu-711777 . License : CC0: No Rights Reserved
- Chilean Flamingo. Authored by : Bernard Spragg. NZ. Located at : https://www.flickr.com/photos/volvob12b/24351280217 . License : CC0: No Rights Reserved
- Snowy Owl. Authored by : Kristina Servant. Located at : https://commons.wikimedia.org/wiki/File:Harfang_des_neiges_-_Snowy_owl_(25478289536).jpg . License : CC BY: Attribution
- American Crow. Authored by : Andy Reago & Chrissy McClarren. Located at : https://commons.wikimedia.org/wiki/File:American_Crow_(30681106607).jpg . License : CC BY: Attribution
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Receptors for touch, pressure, pain and temperature are found in the skin. Receptors in the muscles, tendons and joints inform the brain of limb position.
-
The
olfactory organ
in the nose responds to chemicals in the air i.e. smell.
-
Taste buds
on the tongue respond to a limited range of chemicals dissolved in saliva.
-
The eyes are the organs of sight. Spherical
eyeballs
situated in orbits in the skull have walls composed of 3 layers.
-
The tough outer
sclera
protects and holds the shape of the eyeball. At the front it becomes visible as the white of the eye and the transparent
cornea
that allows light to enter the eye.
-
The middle layer is the
choroid
. It most animals it absorbs stray light rays but in nocturnal animal it is reflective to conserve light. At the front of the eye it becomes the
iris
with muscles to control the size of the
pupil
and hence the amount of light entering the eye.
-
The inner layer is the
retina
containing the light receptor cells: the
rods
for black and white vision in dim light and the
cones
for colour and detailed vision. Nerve impulses generated by these cells leave the eye for the brain via the
optic nerve
.
-
The
lens
(with the cornea) helps focus the light rays on the retina. Muscles alter the shape of the lens to allow near and far objects to be focussed.
-
Aqueous humour
fills the space immediately behind the cornea and keeps it in shape and
vitreous humour
, a transparent jelly-like substance, fills the space behind the lens allowing light rays to pass through to the retina.
-
The ear is the organ of hearing and balance.
-
The external
pinna
helps funnel sound waves into the ear and locate the direction of the sound. The sound waves travel down the external
ear canal
to the
eardrum
or
tympanic membrane
causing it to vibrate. This vibration is transferred to the
auditory ossicles
of the middle ear which themselves transfer it to the inner ear. Here receptors in the
cochlea
respond by generating nerve impulses that travel to the brain via the
auditory
(acoustic) nerve.
-
The
Eustachian tube
connects the middle ear with the pharynx to equalise air pressure on either side of the tympanic membrane.
-
The
vestibular organ
of the inner ear is concerned with maintaining balance and posture. It consists of the
semicircular canals
and the
otolith organs
.


5.6: Chapter 5 Exercises
P5.1 (8 pts)
Suppose I am managing a system of n cell phone sites. A site consists of ‘antennas and electronic communications equipment placed on a radio mast or tower to create a cell in a cellular network.’ I have records of the age of the electronic equipment (\(a_i\) where \(a\) is the current age of the site \(i\)) and a physical condition assessment rating (\(r_i\) where \(r\) is the condition rating index for a site \(i\) on a scale of 1 to 5 with 1 being excellent) of the physical systems each year. I also have a measure of the importance of each site, \(t_i\) where \(t\) is the amount of cellular traffic at a particular site \(i\). In each year, routine maintenance is performed at each site. I can also choose to rehabilitate the physical site (antenna towers, etc.) (which would move the site to condition 2, replace the electronic components (which would also move the site to condition 2), or do both physical rehabilitation and electronic component replacement (which would move the site to condition 1). Each of these actions has an associated cost, denoted \(c_{ij}\) where \(i\) indicates a particular site \(i\) and \(j\) is one of the management strategies.
Formulate a linear programming decision model that would select the best management action for each site in the coming year. ‘Formulate’ means to write out the problem equations. Define appropriate decision and other variables. Your objective is to minimize the sum over all sites of site condition multiplied by importance of each site. Your constraints are an allowable budget and a requirement that the electronics must be replaced if the age is greater than 6 years old.
P5.2 (4 pts)
Suppose you wish to minimize the cost of delivering ethanol from a set of production facilities with a maximum production supply \(S_i\) where \(i\) goes from 1 to \(n\), to a set of metropolitan petroleum mixing facilities (as ethanol is mixed with gasoline) with required amounts \(P_j\) where \(j\) goes from 1 to \(m\). Assume the cost of transportation from a production facility to a mixing facility is \(C_{ij}\).
a. Formulate a linear program problem to serve the required demand with the least cost.
b. What might cause your linear program to be infeasible for the solution?
P5.3 (8 pts)
Let us try an application of a roadway management system optimization model. Suppose I have a small roadway network with 10 links as shown below. In this example, we will just number links (rather than naming them by beginning and endpoints) and consider three action possibilities with forecast pavement conditions post-action as shown. Pavement condition varies from 1 to 7, with 7 excellent. This problem is sufficiently small that in can be solved with the add-in solver program in EXCEL.
| Link | Length | Average Daily Traffic | PCI Do-Nothing | PCI with Main | Maintenance Cost | Rehabilitation Cost | PCI with Rehab. |
| 1 | 5 | 10 | 4 | 5 | 5 | 16 | 7 |
| 2 | 4 | 13 | 3 | 4 | 4 | 15 | 7 |
| 3 | 3 | 12 | 3 | 4 | 3 | 10 | 7 |
| 4 | 6 | 11 | 2 | 3 | 6 | 20 | 7 |
| 5 | 7 | 25 | 5 | 6 | 7 | 22 | 7 |
| 6 | 5 | 50 | 4 | 5 | 5 | 20 | 7 |
| 7 | 4 | 40 | 3 | 4 | 4 | 15 | 7 |
| 8 | 3 | 20 | 3 | 4 | 3 | 10 | 7 |
| 97 | 8 | 15 | 2 | 3 | 8 | 28 | 7 |
| 10 | 2 | 10 | 1 | 2 | 2 | 6 | 7 |
a. Your objective function will have 30 terms, corresponding to the 10 links multiplied by three possible action decision variables: do-nothing, maintenance or rehabilitation. Each term is the product of length, average daily traffic, forecast pavement condition index (PCI) and a decision variable and divided by the sum of the product of length times average daily traffic. Write out your complete problem formulation, including definitions of variables, the various terms in your objective function, and your various constraints (including non-negativity and integral restrictions).
b. Find optimal
solutions for budgets of 40 and 100. What do you conclude about the
maintenance and rehabilitation strategies from your results?
c. Do either of your optimal solutions have
a fractional decision variable value? What could you do about this
in practice knowing that costs and pavement conditions are all
uncertain?
d. Do you think this problem formulation
and data are reasonable? Why or why not?
P5.4 (4 pts)
Let us couple a linear programming problem with a Markov deterioration model. Suppose you have components with three possible States: 1 – good, 2 – ok, 3 – poor. You have one possible action: moves to state 1 with probability 1 at cost ci for component i. State transition probabilities with no action are: p11 = .8, p12=.2, p22 = .8, p23 = .2, p33 = 1. others zero. You have a budget B for the year and current conditions are described by a vector \(si\). Formulate problem to minimize the average condition of all components at end of the year.
P5.5 (8 pts)
The facility manager of a plant is attempting to devise a shift pattern for his workforce. Each day of every working week is divided into three eight-hour shift periods (00:01-08:00, 08:01-16:00, 16:01-24:00) denoted by night, day and late respectively. The plant must be manned at all times and the minimum number of workers required for each of these shifts over any working week is as below:
-
Mon Tues Wed Thur Fri Sat Sun
- Night 5 3 2 4 3 2 2
- Day 7 8 9 5 7 2 5
- Late 9 10 10 7 11 2 2
-
The union agreement governing acceptable shifts for workers is
as follows:
- Each worker is assigned to work either a night shift or a day shift or a late shift and once a worker has been assigned to a shift they must remain on the same shift every day that they work.
- Each worker works four consecutive days during any seven day period.
- In total there are currently 60 workers.
- Formulate an optimization problem to minimize the number of workers in the labor pool.


2 .
What are the eight rights of medication administration?
3 .
What three systems of measurement are commonly used for medication dosing? Which system of measurement is the most accurate?
4 .
Order: Ibuprofen (Advil) 400 mg PO Q4 PRN mild pain. Supplied: Ibuprofen (Advil) 200 mg tablets. How many tablets should the nurse administer?
5 .
Order: Potassium chloride 30 mEq PO × 1 dose. Supplied: 40 mEq/5 mL. How many milliliters should the nurse administer?
6 .
Order: Cefprozil (Cefzil) 15 mg/kg/day PO BID. Supplied: 125 mg/5 mL. Patient weight: 45 lb. How many milliliters should be administered per dose?
7 .
Why is it important for documentation of medication administration to be accurate?
8 .
What actions should the nurse take when a patient refuses a medication?


36.3: Xylem Transport
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Most plants secure the water and minerals they need from their roots. The path taken is:
\[\text{soil} \rightarrow \text{roots} \rightarrow \text{stems} \rightarrow \text{leaves}\]
The minerals (e.g., K + , Ca 2+ ) travel dissolved in the water (often accompanied by various organic molecules supplied by root cells), but less than 1% of the water reaching the leaves is used in photosynthesis and plant growth. Most of it is lost in transpiration, which serve two useful functions- it provides the force for lifting the water up the stems and it cools the leaves. Water and minerals enter the root by separate paths which eventually converge in the stele.
The Pathway of Water and Minerals
Soil water enters the root through its epidermis. It appears that water then travels in both the cytoplasm of root cells - called the symplast (i.e., it crosses the plasma membrane and then passes from cell to cell through plasmodesmata) and in the nonliving parts of the root - called the apoplast (i.e., in the spaces between the cells and in the cells walls themselves. This water has not crossed a plasma membrane. However, the inner boundary of the cortex, the endodermis, is impervious to water because of a band of lignified matrix called the casparian strip. Therefore, to enter the stele, apoplastic water must enter the symplasm of the endodermal cells. From here it can pass by plasmodesmata into the cells of the stele. Once inside the stele, water is again free to move between cells as well as through them. In young roots, water enters directly into the xylem vessels and/or tracheids. These are nonliving conduits so are part of the apoplast.
Once in the xylem, water with the minerals that have been deposited in it (as well as occasional organic molecules supplied by the root tissue) move up in the vessels and tracheids. At any level, the water can leave the xylem and pass laterally to supply the needs of other tissues. At the leaves, the xylem passes into the petiole and then into the veins of the leaf. Water leaves the finest veins and enters the cells of the spongy and palisade layers. Here some of the water may be used in metabolism, but most is lost in transpiration.
Minerals enter the root by active transport into the symplast of epidermal cells and move toward and into the stele through the plasmodesmata connecting the cells. They enter the water in the xylem from the cells of the pericycle (as well as of parenchyma cells surrounding the xylem) through specialized transmembrane channels.
What Forces Water Through the Xylem?
Observations
- The mechanism is based on purely physical forces because the xylem vessels and tracheids are lifeless.
- Roots are not needed. This was demonstrated over a century ago by a German botanist who sawed down a 70-ft (21 meters) oak tree and placed the base of the trunk in a barrel of picric acid solution. The solution was drawn up the trunk, killing nearby tissues as it went.
- However, leaves are needed. When the acid reached the leaves and killed them, the upward movement of water ceased.
- Removing a band of bark from around the trunk - a process called girdling - does not interrupt the upward flow of water. Girdling removes only the phloem, not the xylem, and so the foliage does not wilt. (In due course, however, the roots - and thus the entire plant - will die because the roots cannot receive any of the food manufactured by the leaves.)
Transpiration-Pull
In 1895, the Irish plant physiologists H. H. Dixon and J. Joly proposed that water is pulled up the plant by tension (negative pressure) from above. As we have seen, water is continually being lost from leaves by transpiration. Dixon and Joly believed that the loss of water in the leaves exerts a pull on the water in the xylem ducts and draws more water into the leaf. But even the best vacuum pump can pull water up to a height of only 34 ft (10.4 m) or so. This is because a column of water that high exerts a pressure of ~15 lb/in 2 (103 kilopascals, kPa) just counterbalanced by the pressure of the atmosphere. How can water be drawn to the top of a sequoia (the tallest is 370 feet [113 meters] high)? Taking all factors into account, a pull of at least 270 lb/in 2 (~1.9 x 10 3 kPa) is probably needed.
The answer to the dilemma lies the cohesion of water molecules; that is the property of water molecules to cling to each through the hydrogen bonds they form. When ultrapure water is confined to tubes of very small bore, the force of cohesion between water molecules imparts great strength to the column of water. It has been reported that tensions as great as 3000 lb/in 2 (21 x 10 3 kPa) are needed to break the column, about the value needed to break steel wires of the same diameter. In a sense, the cohesion of water molecules gives them the physical properties of solid wires. Because of the critical role of cohesion, the transpiration-pull theory is also called the cohesion theory .
support for Cohesion theory
- If sap in the xylem is under tension, we would expect the column to snap apart if air is introduced into the xylem vessel by puncturing it. This is the case.
- If the water in all the xylem ducts is under tension, there should be a resulting inward pull (because of adhesion) on the walls of the ducts. This inward pull in the band of sapwood in an actively transpiring tree should, in turn, cause a decrease in the diameter of the trunk.
- The graph shows the results of obtained by D. T. MacDougall when he made continuous measurements of the diameter of a Monterey pine. The diameter fluctuated on a daily basis reaching its minimum when the rate of transpiration reached its maximum (around noon)
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The rattan vine may climb as high as 150 ft (45.7 m) on the trees of the tropical rain forest in northeastern Australia to get its foliage into the sun. When the base of a vine is severed while immersed in a basin of water, water continues to be taken up. A vine less than 1 inch (2.5 cm) in diameter will "drink" water indefinitely at a rate of up to 12 ml/minute.
If forced to take water from a sealed container, the vine does so without any decrease in rate, even though the resulting vacuum becomes so great that the remaining water begins to boil spontaneously. (The boiling temperature of water decreases as the air pressure over the water decreases, which is why it takes longer to boil an egg in Denver than in New Orleans.)
- Transpiration-pull enables some trees and shrubs to live in seawater. Seawater is markedly hypertonic to the cytoplasm in the roots of the red mangrove ( Rhizophora mangle ), and we might expect water to leave the cells resulting in a loss in turgor and wilting. In fact, the remarkably high tensions on the order of 500–800 lb/in 2 ( ~3 to 5 thousand kPa) in the xylem can pull water into the plant against this osmotic gradient. So mangroves literally desalt seawater to meet their needs.
Problems with the theory
When water is placed under a high vacuum, any dissolved gases come out of solution as bubbles (as we saw above with the rattan vine) - this is called cavitation . Any impurities in the water enhance the process. So measurements showing the high tensile strength of water in capillaries require water of high purity - not the case for sap in the xylem. So might cavitation break the column of water in the xylem and thus interrupt its flow? Probably not so long as the tension does not greatly exceed 270 lb/in 2 (~1.9 x 10 3 kPa).
By spinning branches in a centrifuge, it has been shown that water in the xylem avoids cavitation at negative pressures exceeding 225 lb/in 2 (~1.6 x 10 3 kPa). And the fact that sequoias can successfully lift water 358 ft (109 m) - which would require a tension of 270 lb/in 2 (~1.9 x 10 3 kPa) - indicates that cavitation is avoided even at that value. However, such heights may be approaching the limit for xylem transport. Measurements close to the top of the tallest living sequoia (370 ft [=113 m] high) show that the high tensions needed to get water up there have resulted in smaller stomatal openings, causing lower concentrations of CO 2 in the needles, causing reduced photosynthesis, causing reduced growth (smaller cells and much smaller needles). (Reported by Koch, G. W. et al. , in Nature , 22 April 2004.) So the limits on water transport limit the ultimate height which trees can reach. The tallest tree ever measured, a Douglas fir, was 413 ft. (125.9 meters) high.
Root Pressure
When a tomato plant is carefully severed close to the base of the stem, sap oozes from the stump. The fluid comes out under pressure which is called root pressure. Root pressure is created by the osmotic pressure of xylem sap which is, in turn, created by dissolved minerals and sugars that have been actively transported into the apoplast of the stele.
One important example is the sugar maple when, in very early spring, it hydrolyzes the starches stored in its roots into sugar. This causes water to pass by osmosis through the endodermis and into the xylem ducts. The continuous inflow forces the sap up the ducts.
Although root pressure plays a role in the transport of water in the xylem in some plants and in some seasons, it does not account for most water transport.
- Few plants develop root pressures greater than 30 lb/in 2 (207 kPa), and some develop no root pressure at all.
- The volume of fluid transported by root pressure is not enough to account for the measured movement of water in the xylem of most trees and vines.
- Those plants with a reasonably good flow of sap are apt to have the lowest root pressures and vice versa.
- The highest root pressures occur in the spring when the sap is strongly hypertonic to soil water, but the rate of transpiration is low. In summer, when transpiration is high and water is moving rapidly through the xylem, often no root pressure can be detected.
So although root pressure may play a significant role in water transport in certain species (e.g., the coconut palm) or at certain times, most plants meet their needs by transpiration-pull.


7.3: Competitive Advantage
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- Ly-Huong T. Pham, Tejal Desai-Naik, Laurie Hammond, & Wael Abdeljabbar
- ASCCC Open Educational Resources Initiative (OERI)
What do Walmart, Apple, and McDonald’s have in common?
All three businesses have a Competitive advantage. What does it mean when a company has a competitive advantage? What are the factors that play into it? According to Michael Porter in his book “Competitive Advantage: Creating and Sustaining Superior Performance,” a company is said to have a competitive advantage over its rivals when it can sustain profits that exceed the industry's average. Porter identified two basic types of competitive advantage:
- Cost advantage : When the firm can deliver the same benefits as competitors but at a lower cost. McDonald's and Walmart both utilize economies of scale to maintain their cost advantage.
- Differentiation advantage : When a firm can deliver benefits that exceed those of competing products. Apple’s innovative products that complement each other and share the same operating system offer a unique product that gives consumers a sense of exclusivity, and their trade-in programs build consumer loyalty.
The question, then, is: How can information technology be a factor in achieving Competitive advantage? We will explore this question by using:
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Two analysis tools from Porter’s book “Competitive advantage: Creating and Sustaining Superior Performance:
- The value chain
- The Five Forces model.
- Porter’s analysis in his 2001 article “Strategy and the Internet.”
The Value Chain
In his book, Porter analyzes the basis of competitive advantage and describes how a company can achieve it using the value chain as a framework. A value chain is a step-by-step business model transforming a product or service from an idea (i.e., materials) to reality ( i.e., products or services). Value chains help increase a business’s efficiency so the business can deliver the most value(i.e., profit) for the least possible cost. Each step (or activity) in the value chain contributes to a product or service's overall value. While the value chain may not be a perfect model for every type of company, it does provide a way to analyze just how a company is producing value.
The value chain is made up of two sets of activities: primary activities and support activities. We will briefly examine these activities and discuss how information technology can create value by contributing to cost advantage or differentiation advantage, or both.
The primary activities are the functions that directly impact the creation of a product or service, its sales, and after-sales service. The goal of the primary activities is to add more value than they cost. The primary activities are:
- Inbound logistics : Purchasing, Receiving, and storing raw materials. Information technology can make these processes more efficient, such as with supply-chain management systems, which allow the suppliers to manage their own inventory. Starbucks has company-appointed coffee buyers that select the finest quality coffee beans from producers in Latin America, Africa, and Asia.
- Operations : Any part of a business involved in converting the raw materials into the final products or services is part of operations. From manufacturing to business process management (covered in chapter 8), information technology can provide more efficient processes and increase innovation through information flows.
- Outbound logistics : These functions include order processing and warehousing required to get the product out to the customer. As with inbound logistics, IT can improve processes, such as allowing for real-time inventory checks. IT can also be a delivery mechanism itself.
- Marketing/Sales : The functions that will entice buyers to purchase the products (advertising, salesforce) are part of sales and marketing. Information technology is used in almost all aspects of this activity. From online advertising to online surveys, IT can innovate product design and reach customers like never before. The company website can be a sales channel itself.
- Service : The functions a business performs after the product has been purchased, such as installation, customer support, complaint resolution, and repair to maintain and enhance its value, are part of the service activity. Service can be enhanced via technology as well, including support services through websites and knowledge bases.
The support activities are the functions in an organization that support and cut across all primary activities. The support activities are:
- Firm infrastructure : Organizational functions such as finance, accounting, ERP Systems (covered in chapter 9), and quality control, all of which depend on information technology.
- Technology development : Technological advances and innovations support the primary activities. These advances are then integrated across the company to add value in different departments. Information technology would fall specifically under this activity.
- Procurement: Acquiring the raw materials used in the creation of products and services is called procurement. Business-to-business e-commerce can be used to improve the acquisition of materials.
A value chain is a powerful tool in analyzing and breaking down a company into its relevant activities that result in higher prices and lower cost, by understanding how these activities are connected and the company’s strategic objectives, companies can identify their core competencies and insight into how information technology can be used to achieve a competitive advantage.
Look at this example of the Starbucks value chain model analysis that includes a short video by Prableen Bajpai: Analyzing Starbucks Value Chain Model .
Porter’s Five Forces
Porter recognized that other factors could impact a company’s profit in addition to competition from their rivals. He developed the “five forces'' model as a framework for analyzing the competition in an industry and its strengths and weaknesses. The model consists of five elements, each of which plays a role in determining an industry's average profitability.
In 2001, Porter wrote an article entitled ” Strategy and the Internet , ” in which he takes this model and looks at how the Internet(and IT) impacts an industry's profitability. Although the model's details differ from one industry to another, its general structure of the five forces is universal. Let’s have a look at how the internet plays a role in Porter’s five forces model:
- Threat of New Entrants : The easier it is to enter an industry, the tougher it will be to profit in that industry. The Internet has an overall effect of making it easier to enter industries. Traditional barriers such as the need for a physical store and sales force to sell goods and services are drastically reduced. Dot-coms multiplied for that very reason: All a competitor has to do is set up a website. The geographical reach of the internet enables distant competitors to compete more directly with a local firm. For example, a manufacturer in Northern California may now have to compete against a manufacturer in the Southern United States, where wages are lower.
- Threat of Substitute Products : How easily can a product or service be replaced with something else? The more types of products or services there can meet a particular need, and the less profitability will be in an industry. For example, the advent of the mobile phone has replaced the need for pagers. The Internet has made people more aware of substitute products, driving down industry profits in those industries being substituted. Any industry in which digitized information can replace material goods such as books, music, software is at particular risk ( Think, for example, Amazon’s Kindle and Spotify) .
- Bargaining Power of Suppliers : Companies can more easily find alternative suppliers and compare prices more easily. When a sole supplier exists, then the company is at the mercy of the supplier. For example, if only one company makes the controller chip for a car engine, that company can control the price, at least to some extent. The Internet has given companies access to more suppliers, driving down prices. On the other hand, suppliers now also have the ability to sell directly to customers. As companies use IT to integrate their supply chain, participating suppliers will prosper by locking customers and increasing switching costs.
- Bargaining Power of Customers : A company that is the sole provider of a unique product has the ability to control pricing. But the Internet has given customers access to information about products and more options (small and big business) to choose from.
- Threat of Substitute Products : The more competitors in an industry, the bigger a factor price becomes. The visibility of internet applications on the Web makes proprietary systems more difficult to keep secret. It is straightforward to copy technology, so innovations will not last that long. For example, Sony Reader was released in 2006, followed by Amazon Kindle in 2007, and just two years later, Barnes and Noble Nook, which was the best-selling unit in the US before iPad (with built-in reading app iBooks) hit the market in 2010. (Wikipedia: E-Reader, 2020)
According to this model, the company's average profitability depends on the five forces' collective strength. If the five forces are intense, for example, in the airline industry, almost no company makes a huge profit. If the forces are mild, for example, the soft drink industry, there is room for higher profits. The Internet provides better opportunities for companies to establish strategic advantage by boosting efficiency in various ways, as we will see in the next section. However, the internet also tends to dampen suppliers' bargaining power and increase the threat of substitute products by making it easier for buyers and sellers to do business. Thus, the Internet (and, by extension, information technology in general) has the overall impact of increasing competition and lowering profitability. This is the great paradox of the internet.
While the Internet has certainly produced many big winners, the overall winners have been the consumers, who have been given an ever-increasing market of products and services and lower prices.
References
Bajpai, P (2020). Analyzing Starbucks Value Chain Model . Retrieved August 16, 2020, from https://www.investopedia.com/articles/investing/103114/starbucks-example-value-chain-model.asp
Porter, M. (2001). Strategy and the Internet. Harvard Business Review. Retrieved August 20, 2020, from http://hbswk.hbs.edu/item/2165.html